A gadolinium and pH-sensitive hyperpolarization-activated cation current in acutely isolated single neurones from Fasciola hepatica

Parasitology ◽  
2002 ◽  
Vol 125 (5) ◽  
pp. 423-430 ◽  
Author(s):  
H. S. KIM ◽  
K. Y. KAM ◽  
P. D. RYU ◽  
S. J. HONG ◽  
J. S. JEON ◽  
...  
Keyword(s):  
Fasciola Hepatica ◽  
Ph Sensitive ◽  
Membrane Potentials ◽  
Electrophysiological Properties ◽  
Extracellular Acidosis ◽  
Cation Current ◽  
Whole Cell Patch Clamp ◽  
Dependent Inactivation ◽  
Single Neurones ◽  
Ph Range

Fasciola hepatica, a parasitic flatworm belonging to the Class Trematoda, is one of the first metazoan groups to possess a centralized nervous system. However, the electrophysiological properties of neurones in F. hepatica are largely unknown. In the present study, we acutely isolated viable neurones from F. hepatica and characterized their electrophysiological properties. A hyperpolarization-activated cation current was recorded in the cells using the whole-cell patch-clamp. The current was found to be activated slowly at membrane potentials negative to 0 mV and did not display any time-dependent inactivation. This current was reduced by 1 mM Gd3+ to the level of the leak current, while 3 mM of Cs+ had no effect. However, the current was inhibited by extracellular acidosis in the pH range 7.0–7.8, and the membrane potentials of these cells were depolarized by extracellular alkalosis in the pH range of 5.8 to 8.2. Gd3+ (1 mM), which inhibited the pH-sensitive hyperpolarization-activated cation current, also hyperpolarized the cells. In summary, we isolated single neurones from F. hepatica, and these were found to express a pH-sensitive hyperpolarization-activated cation current. This current may participate in the membrane depolarization of F. hepatica neurones during alkaline challenge.

scholarly journals Stabilization and Release of Palm Tocotrienol Emulsion Fabricated Using pH-Sensitive Calcium Carbonate

Foods ◽  
2021 ◽  
Vol 10 (2) ◽  
pp. 358
Author(s):  
Phui Yee Tan ◽  
Beng Ti Tey ◽  
Eng Seng Chan ◽  
Oi Ming Lai ◽  
Hon Weng Chang ◽  
...  
Keyword(s):  
Calcium Carbonate ◽  
Droplet Size ◽  
Entrapment Efficiency ◽  
Ph Sensitive ◽  
Emulsion System ◽  
Ph Responsive ◽  
Small Droplet ◽  
Homogenization Time ◽  
Oil In Water ◽  
Ph Range

Calcium carbonate (CaCO3) has been utilized as a pH-responsive component in various products. In this present work, palm tocotrienols-rich fraction (TRF) was successfully entrapped in a self-assembled oil-in-water (O/W) emulsion system by using CaCO3 as the stabilizer. The emulsion droplet size, viscosity and tocotrienols entrapment efficiency (EE) were strongly affected by varying the processing (homogenization speed and time) and formulation (CaCO3 and TRF concentrations) parameters. Our findings indicated that the combination of 5000 rpm homogenization speed, 15 min homogenization time, 0.75% CaCO3 concentration and 2% TRF concentration resulted in a high EE of tocotrienols (92.59–99.16%) and small droplet size (18.83 ± 1.36 µm). The resulting emulsion system readily released the entrapped tocotrienols across the pH range tested (pH 1–9); with relatively the highest release observed at pH 3. The current study presents a potential pH-sensitive emulsion system for the entrapment and delivery of palm tocotrienols.

scholarly journals A CACNA1A variant associated with trigeminal neuralgia alters the gating of Cav2.1 channels

2021 ◽  
Vol 14 (1) ◽  
Author(s):  
Eder Gambeta ◽  
Maria A. Gandini ◽  
Ivana A. Souza ◽  
Laurent Ferron ◽  
Gerald W. Zamponi
Keyword(s):  
Trigeminal Neuralgia ◽  
Missense Mutation ◽  
Neurotransmitter Release ◽  
Trigeminal System ◽  
Wild Type ◽  
Calcium Dependent ◽  
Whole Cell Patch Clamp ◽  
C Terminus ◽  
Dependent Inactivation

AbstractA novel missense mutation in the CACNA1A gene that encodes the pore forming α1 subunit of the CaV2.1 voltage-gated calcium channel was identified in a patient with trigeminal neuralgia. This mutation leads to a substitution of proline 2455 by histidine (P2455H) in the distal C-terminus region of the channel. Due to the well characterized role of this channel in neurotransmitter release, our aim was to characterize the biophysical properties of the P2455H variant in heterologously expressed CaV2.1 channels. Whole-cell patch clamp recordings of wild type and mutant CaV2.1 channels expressed in tsA-201 cells reveal that the mutation mediates a depolarizing shift in the voltage-dependence of activation and inactivation. Moreover, the P2455H mutant strongly reduced calcium-dependent inactivation of the channel that is consistent with an overall gain of function. Hence, the P2455H CaV2.1 missense mutation alters the gating properties of the channel, suggesting that associated changes in CaV2.1-dependent synaptic communication in the trigeminal system may contribute to the development of trigeminal neuralgia.

Construction of a pH-sensitive self-assembly in aqueous solutions based on a dansyl-modified β-cyclodextrin

Soft Matter ◽  
2021 ◽  
Author(s):  
Bing Jiang ◽  
Yu Liu ◽  
Linlin Zhao ◽  
Li Zhao ◽  
Ce Wang ◽  
...  
Keyword(s):  
Aqueous Solutions ◽  
Self Assembly ◽  
Ph Sensitive ◽  
Ph Responsive ◽  
Ph Range

Here we present a pH-responsive self-assembly based on a β-cyclodextrin (β-CD) derivative bearing a dansyl terminus (βCD-C6-Dns). Vesicular structures were formed over the entire studied pH range (8.5-0.7); however, the...

Properties of cAMP-dependent and Ca(2+)-dependent whole cell Cl- conductances in rat epididymal cells

1993 ◽  
Vol 264 (4) ◽  
pp. C794-C802 ◽  
Author(s):  
S. J. Huang ◽  
W. O. Fu ◽  
Y. W. Chung ◽  
T. S. Zhou ◽  
P. Y. Wong
Keyword(s):  
Cystic Fibrosis ◽  
Transmembrane Conductance Regulator ◽  
Transmembrane Conductance ◽  
Whole Cell ◽  
Cyclic Monophosphate ◽  
Cation Current ◽  
Whole Cell Patch Clamp ◽  
Current Voltage ◽  
Clamp Condition ◽  
Cl Conductance

Single rat epididymal cell studied under whole cell patch-clamp condition responded to 8-(4-chlorophenylthio)-adenosine 3',5'-cyclic monophosphate (CPT-cAMP) (500 microM) and to ionomycin (1 microM) by an increase in whole cell conductance. A major part of the stimulated current was carried by Cl-, although a small part was due to nonselective cation current. After elimination of the cation current component by using impermeant cation, the cells revealed different Cl- conductance properties in response to adenosine 3',5'-cyclic monophosphate (cAMP) and ionomycin. The cAMP-stimulated Cl- conductance was independent of time and voltage and showed a linear current-voltage relationship. The anion permselectivity was NO3- > Br- > Cl- approximately I- >> SO(4)2-. The ionomycin-stimulated Cl- conductance showed marked time and voltage dependency. In contrast to the cAMP-induced anion permselectivity, the ionomycin-induced anion permselectivity was I- > Br- approximately NO3- > Cl- >> SO(4)2-. These results indicate that the epididymal epithelial cells exhibit different Cl- conductances sensitive to cAMP and Ca2+. The cAMP-activated conductance has properties resembling the type associated with the cystic fibrosis transmembrane conductance regulator found in cystic fibrosis-affected epithelia. This finding supports the notion that the epididymis is a cystic fibrosis epithelium.

Complexity of the outward K+ current of the rat megakaryocyte

1997 ◽  
Vol 272 (5) ◽  
pp. C1525-C1531 ◽  
Author(s):  
E. Romero ◽  
R. Sullivan
Keyword(s):  
K Channel ◽  
Delayed Rectifier ◽  
Channel Blockers ◽  
Excitable Cells ◽  
Electrophysiological Properties ◽  
Relative Contribution ◽  
Delayed Rectifier Current ◽  
Dependent Inactivation ◽  
Voltage Dependent ◽  
K Current

Megakaryocytes isolated from rat bone marrow express a voltage-dependent, outward K+ current with complex kinetics of activation and inactivation. We found that this current could be separated into at least two components based on differential responses to K+ channel blockers. One component, which exhibited features of the "transient" or "A-type" K+ current of excitable cells, was more strongly blocked by 4-aminopyridine (4-AP) than by tetrabutylammonium (TBA). This current, which we designated as "4-AP-sensitive" current, activated rapidly at potentials more positive than -40 mV and subsequently underwent rapid voltage-dependent inactivation. A separate current that activated slowly was blocked much more effectively by TBA than by 4-AP. This "TBA-sensitive" component, which resembled a typical delayed rectifier current, was much more resistant to voltage-dependent inactivation. The relative contribution of each of these components varied from cell to cell. The effect of charybdotoxin was similar to that of 4-AP. Our data indicate that the voltage-dependent K+ current of resting megakaryocytes is more complex than heretofore believed and support the emerging concept that megakaryocytes possess intricate electrophysiological properties.

Effects of thyroid hormone on action potential and repolarizing currents in rat ventricular myocytes

2000 ◽  
Vol 278 (2) ◽  
pp. E302-E307 ◽  
Author(s):  
Zhuo-Qian Sun ◽  
Kaie Ojamaa ◽  
William A. Coetzee ◽  
Michael Artman ◽  
Irwin Klein
Keyword(s):  
Action Potential ◽  
Cardiac Electrophysiology ◽  
Ventricular Myocytes ◽  
Outward Current ◽  
Mechanisms Of Action ◽  
Transient Outward Current ◽  
Prolonged Action ◽  
Electrophysiological Properties ◽  
Whole Cell Patch Clamp ◽  
Prolonged Action Potential Duration

Thyroid hormones play an important role in cardiac electrophysiology through both genomic and nongenomic mechanisms of action. The effects of triiodothyronine (T3) on the electrophysiological properties of ventricular myocytes isolated from euthyroid and hypothyroid rats were studied using whole cell patch clamp techniques. Hypothyroid ventricular myocytes showed significantly prolonged action potential duration (APD90) compared with euthyroid myocytes, APD90 of 151 ± 5 vs. 51 ± 8 ms, respectively. Treatment of hypothyroid ventricular myocytes with T3 (0.1 μM) for 5 min significantly shortened APD by 24% to 115 ± 10 ms. T3 similarly shortened APD in euthyroid ventricular myocytes, but only in the presence of 4-aminopyridine (4-AP), an inhibitor of the transient outward current ( I to), which prolonged the APD by threefold. Transient outward current ( I to) was not affected by the acute application of T3 to either euthyroid or hypothyroid myocytes; however, I to density was significantly reduced in hypothyroid compared with euthyroid ventricular myocytes.

Possible contribution of long open state to noninactivating Ca2+ current in detrusor cells

1995 ◽  
Vol 269 (1) ◽  
pp. C48-C54 ◽  
Author(s):  
S. Nakayama ◽  
A. F. Brading
Keyword(s):  
Smooth Muscles ◽  
Activation Parameters ◽  
Patch Clamp Technique ◽  
Inactivation Curve ◽  
Voltage Range ◽  
Channel Current ◽  
Whole Cell Patch Clamp ◽  
Dependent Inactivation ◽  
Window Current ◽  
Isolated Smooth Muscle Cells

The whole cell patch-clamp technique was used to measure Ca2+ current in isolated smooth muscle cells from guinea pig urinary bladder. Noniactivating Ca2+ channel current was modeled incorporating the long open state of the Ca2+ channel. When inactivation was examined over a wide voltage range, a completely U-shaped curve was obtained. Lack of inactivation at +80 mV could be attributed to the long open state induced by large depolarization as well as to minimal Ca2+ influx and Ca(2+)-dependent inactivation. Activation parameters were obtained by comparing the amplitudes of conditioned (by +80 mV, 5 s) and unconditioned test potentials. With the use of the activation curve and the U-shaped inactivation curve, a noninactivating current that peaks around +20 mV was obtained. This current is composed of a so-called “window” current and a persistent current brought about by the long open state. Differences in the voltage dependence of the development of the long open state in various smooth muscles, as well as differences in the equilibrium constant between open and inactivated states, could underlie the different patterns of contractile behavior that characterize smooth muscles.

scholarly journals Electrophysiological Diversity of Layer 5 Pyramidal Cells in the Prefrontal Cortex of the Rhesus Monkey: In Vitro Slice Studies

2007 ◽  
Vol 98 (5) ◽  
pp. 2622-2632 ◽  
Author(s):  
Yu-Ming Chang ◽  
Jennifer I. Luebke
Keyword(s):  
Prefrontal Cortex ◽  
Rhesus Monkey ◽  
Spike Train ◽  
Pyramidal Cells ◽  
Cell Types ◽  
Dendritic Morphology ◽  
Firing Patterns ◽  
Electrophysiological Properties ◽  
Whole Cell Patch Clamp

Whole cell patch-clamp recordings were employed to characterize the electrophysiological properties of layer 5 pyramidal cells in slices of the prefrontal cortex (Area 46) of the rhesus monkey. Four electrophysiologically distinct cell types were discriminated based on distinctive repetitive action potential (AP) firing patterns and single AP characteristics: regular-spiking slowly adapting type-1 cells (RS1; 62%), regular-spiking slowly adapting type-2 cells (RS2; 18%), regular-spiking fast-adapting cells (FA; 15%), and intrinsically bursting cells (IB; 5%). These cells did not differ with regard to their location in layer 5 nor in their dendritic morphology. In RS1 cells, AP threshold and amplitude did not change significantly during a 2-s spike train, whereas in RS2 and FA cells, AP threshold increased significantly and AP amplitude decreased significantly during the train. In FA cells, complete adaptation of AP firing was observed within 600 ms. IB cells displayed an all-or-none burst of three to six APs, followed by RS1-type firing behavior. RS1 cells could be further subdivided into three subtypes. Low-threshold spiking (LTS) RS1 cells exhibited an initial doublet riding on a depolarizing potential at the onset of a spike train and a prominent depolarizing afterpotential (DAP); intermediate RS1 cells (IM) exhibited a DAP, but no initial doublet, and non-LTS RS1 cells exhibited neither a DAP nor an initial doublet. RS2 and FA cells did not exhibit a DAP or initial doublets. The distinctive firing patterns of these diverse layer 5 pyramidal cells may reflect different roles played by these cells in the mediation of subcortical neuronal activity by the dorsolateral PFC.

scholarly journals Nonlinear current-voltage relationships in cultured macrophages.

1980 ◽  
Vol 85 (1) ◽  
pp. 160-165 ◽  
Author(s):  
E K Gallin ◽  
D R Livengood
Keyword(s):  
High Resistance ◽  
Membrane Potentials ◽  
Transitional Region ◽  
Stable States ◽  
Excitable Cells ◽  
Electrophysiological Properties ◽  
Current Pulses ◽  
Current Voltage ◽  
Different Types ◽  
Peritoneal Exudate Macrophages

Intracellular recordings of cultured mouse thioglycolate-induced peritoneal exudate macrophages reveal that these cells can exhibit two different types of electrophysiological properties characterized by differences in their current-voltage relationships and their resting membrane potentials. The majority of cells had low resting membrane potentials (-20 to -40 mV) and displayed current-voltage relationships that were linear for inward-going current pulses and rectifying for outward-going pulses. Small depolarizing transients, occurring either spontaneously or induced by current pulses, were seen in some cells with low resting membrane potentials. A second smaller group of cells exhibited more hyperpolarized resting membrane potentials (-60 to -90 mV) and S-shaped current-voltage relationships associated with a high-resistance transitional region. Cells with S-shaped current-voltage relationships sometimes exhibited two stable states of membrane potential on either side of the high-resistance transitional region. These data indicate that macrophages exhibit complex electrophysiological properties often associated with excitable cells.

Characterization of zebrafish (Danio rerio) NCX4: a novel NCX with distinct electrophysiological properties

2009 ◽  
Vol 296 (1) ◽  
pp. C173-C181 ◽  
Author(s):  
Caly On ◽  
Christian R. Marshall ◽  
Steve F. Perry ◽  
Hoa Dinh Le ◽  
Vladimir Yurkov ◽  
...  
Keyword(s):  
Danio Rerio ◽  
Splice Variants ◽  
Inhibitory Peptide ◽  
Electrophysiological Properties ◽  
Outward Currents ◽  
Dependent Inactivation ◽  
Wide Range ◽  
Heterologous Expression Systems ◽  
High Degree ◽  
First Time

Members of the Na+/Ca2+ exchanger (NCX) family are important regulators of cytosolic Ca2+ in myriad tissues and are highly conserved across a wide range of species. Three distinct NCX genes and numerous splice variants exist in mammals, many of which have been characterized in a variety of heterologous expression systems. Recently, however, we discovered a fourth NCX gene ( NCX4), which is found exclusively in teleost, amphibian, and reptilian genomes. Zebrafish ( Danio rerio) NCX4a encodes for a protein of 939 amino acids and shows a high degree of identity with known NCXs. Although knockdown of NCX4a activity in zebrafish embryos has been shown to alter left-right patterning, it has not been demonstrated that NCX4a functions as a NCX. In this study, we 1) demonstrated, for the first time, that this gene encodes for a novel NCX; 2) characterized the tissue distribution of zebrafish NCX4a; and 3) evaluated its kinetic and transport properties. While ubiquitously expressed, the highest levels of NCX4a expression occurred in the brain and eyes. NCX4a exhibits modest levels of Na+-dependent inactivation and requires much higher levels of regulatory Ca2+ to activate outward exchange currents. NCX4a also exhibited extremely fast recovery from Na+-dependent inactivation of outward currents, faster than any previously characterized wild-type exchanger. While this result suggests that the Na+-dependent inactive state of NCX4a is far less stable than in other NCX family members, this exchanger was still strongly inhibited by 2 μM exchanger inhibitory peptide. We demonstrated that a new putative member of the NCX gene family, NCX4a, encodes for a NCX with unique functional properties. These data will be useful in understanding the role that NCX4a plays in embryological development as well as in the adult, where it is expressed ubiquitously.

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